1. Field of the Invention
The present invention relates to a hydraulic circuit having a rotary type pump and a brake apparatus provided with the hydraulic circuit having the rotary type pump.
2. Related Arts
A schematic view of a conventional inner-contact rotary type pump is shown in FIG. 67A. A sectional view taken on line 67B--67B in FIG. 67A is shown in FIG. 67B. As shown in FIG. 67A, an outer rotor 351 and an inner rotor 352 are assembled in a rotor chamber of a casing 350 of the inner-contact rotary type pump. An inner teeth portion 351a is formed on an inner periphery of the outer rotor 351 and an outer teeth portion 352a is formed on an outer periphery of the inner rotor 352. The inner teeth portion 351a and the outer teeth portion 352a are engaged to each other while forming a gap 353 therebetween. As shown in FIG. 67B, a center hole 350a is formed at a center of the casing 350 and a driving shaft 354 to be connected to the inner rotor 352 is inserted into the center hole 350a. The outer rotor 351 is rotatably disposed in the rotor chamber of the casing 350. An inlet port 360 and an outlet port 361 are formed in the rotor chamber of the casing 350, interposing the central axes of the rotors 351, 352 therebetween.
When the pump is driven, the inner rotor 352 rotates with the driving shaft 354. Along with the rotation of the inner rotor 352, the outer rotor 351 also rotates in the same direction as the inner rotor 352 since the outer teeth portion 352a and the inner teeth portion 351a are engaged to each other. During the rotations of the inner and outer rotors 351, 352, the volume of the gap 353 decreases and then increases to its original while the inner and outer rotors 351 and 352 make one rotation. As a result, fluid is drawn in the gap 353 from the inlet port 360 and discharged into the outlet port 361.
To rotate the inner and outer rotors 351, 352 smoothly, a clearance 400 is provided between the casing 350 and the outer rotor 351, inner rotor 352, or driving shaft 354. However, because fluid leakage occurs from the clearance 400, the central hole 350a is sealed by an oil seal 410 to prevent the fluid leakage. In addition, a return path G is provided in the casing 350 to return fluid within the clearance 400 to the inlet port 360. The fluid within the clearance 400 is low in pressure. However, if the fluid cannot escape out of the clearance 400, pressure in the clearance 400 becomes high due to the fluid injected thereinto. For this reason, the return path G is provided and, with the fluid returned to the inlet port 360 therethrough, pressurization of the clearance 400 and fluid leakage to outside can be prevented.
Fluid flows from a high pressure side to a low pressure side. Therefore, if the pressure of fluid within the inlet port 360 is higher than the pressure of fluid within the clearance 400, fluid having leaked into the clearance 400 can not return to the inlet port 360 through the return path G, thereby causing the pressurization of the clearance 400. Further, if the pressure of fluid within the clearance 400 exceeds an allowable pressure of the oil seal 410, fluid leakage to outside occurs.
Therefore, it is a first object of the present invention to provide hydraulic circuit having a rotary type pump which can prevent fluid leakage to outside.
It is a second object of the present invention to provide a brake system which can prevent fluid leakage to outside by using such a hydraulic circuit.